JP5153507B2 - Wireless communication device - Google Patents

Description

  The present invention relates to a wireless communication apparatus, a wireless communication system, and a calibration method for performing calibration between a plurality of antennas.

  In recent years, there is a great demand for high-speed wireless communication, and high-speed wireless communication transmission technology is required. Therefore, recently, a technique in which a transceiver performs high-speed signal transmission using a plurality of antennas has been widely studied. In future mobile communications, an environment in which a base station simultaneously performs spatial multiplexing transmission using a transmission beam to a plurality of terminals is also assumed. Further, if the terminal side also performs appropriate transmission beam forming, it is possible to reduce transmission power required for communication. Therefore, high-accuracy transmission beam forming technology is considered as an important issue in the future.

  Among them, in the TDD (Time Division Duplex) method in which the same frequency is alternately used in the uplink and the downlink, there is an expectation for an advantage that the propagation path reversibility can be used in forming the transmission beam. Usually, the transmitter needs channel information to properly control the transmit beam. At this time, assuming that the ideal channel reversibility can be obtained by the TDD method, the channel state from the transmitter to the receiver can be easily grasped by measuring the channel from the receiver to the transmitter using the pilot signal. .

  However, in reality, although the reversibility is established in the actual propagation path from the antenna end of the transmitter to the antenna end of the receiver, the propagation path (hereinafter referred to as the propagation path measured in the digital domain) due to the difference in characteristics of analog devices in the transceiver circuit. In the measurement propagation path), complete reversibility does not hold. Usually, radio equipment performs propagation path measurement in the digital domain, but in order to use reversibility, calibration is required to compensate for transmission / reception system analog characteristic differences in the radio equipment and maintain reversibility in the measurement propagation path. Become.

  As such a calibration technique, conventionally, for example, a self-calibration technique as disclosed in Patent Document 1 and Non-Patent Document 1 below is known. In these techniques, the transmission / reception system analog characteristic difference between antennas is compensated by transmitting / receiving test signals between a plurality of antennas in a radio.

JP 2006-279668 A K. Nishimori, K. Cho, Y. Takatori, T. Hori, “A novel configuration for realizing automatic calibration of adaptive array using dispersed SPDT switches for TDD systems”, IEICE Trans. On Commun., Vol. E84-B, No .9, pp.2516-2522, Sept. 2001.

  However, according to the conventional self-calibration technique, test signals are transmitted and received between a plurality of antennas in the radio. At this time, calibration can be performed with a weak transmission power, but if another radio exists near the radio to be calibrated, the test signal may interfere with the other radio. . For this reason, there is a problem that the quality of other in-communication signals may deteriorate due to interference from the calibration test signal.

  The present invention has been made in view of the above, and is a wireless communication device capable of reducing interference that a calibration test signal gives to other communication and preventing communication quality deterioration of the other wireless communication device, An object is to obtain a wireless communication system and a calibration method.

In order to solve the above-described problems and achieve the object, the present invention is a wireless communication apparatus having the plurality of antennas that performs self-calibration between the plurality of antennas, and adopts an OFDM method as a digital modulation method. In this case, self-calibration is performed using an OFDM symbol having a shorter symbol time than the OFDM symbol during data communication as a calibration test signal .

According to the invention, to reduce interference test signal for Calibration has on the other communications, it is possible to prevent communication quality deterioration of other wireless communication device, an effect that.

  Hereinafter, embodiments of a wireless communication device, a wireless communication system, and a calibration method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a functional configuration example of a first embodiment of a wireless communication apparatus according to the present invention. In the present embodiment, a terminal 1 will be described as an example of a wireless communication apparatus according to the present invention. As illustrated in FIG. 1, the terminal 1 according to the present embodiment includes antennas 11-1 and 11-2, signal reception units 12-1 and 12-2 that perform predetermined reception processing on reception signals, and transmission signals. Signal transmission units 13-1 and 13-2 that perform predetermined transmission processing, a frame detection unit 14 that detects upstream or downstream frames, and a calibration control unit 15 that controls self-calibration are provided. In this embodiment, a configuration including two antennas, a signal receiving unit, and a signal transmitting unit is shown, but any number of these components may be provided as long as there are two or more.

  FIGS. 2-1 and 2-2 are diagrams illustrating the execution timing of self-calibration (hereinafter referred to as calibration) and the influence on other terminals. Terminals 1-1 and 1-2 in the figure are terminals having functions similar to those of terminal 1 in FIG. 1, and both terminals are close to each other. The terminal 1-2 communicates with the base station 2 and the terminal 1-1 performs self-calibration. Here, the terminal 1-2 is a terminal having the same function as that of the terminal 1 of FIG. 1, but is not limited thereto, and may be a terminal having another configuration, or a base station 2 other than the terminal. It may be a wireless device that communicates with.

  In general, the transmission power of the test signal when the terminal performs calibration is weak, and when another radio is far away from the terminal to some extent, the interference that the test signal has on the other radio due to distance attenuation is Very small. However, when another wireless device is present at a short distance from the terminal that performs calibration, even if the test signal is weak, the other wireless device receives it as a large interference power.

  In the present embodiment, uplink (transmission from terminals 1-1 and 1-2 to base station 2) and downlink (transmission from base station 2 to terminals 1-1 and 1-2) using the same frequency band. ) Is assumed to be switched alternately. FIG. 2-1 illustrates an example in which the terminal 1-1 performs calibration in the downlink, and FIG. 2-2 illustrates an example in which the terminal 1-1 performs calibration in the uplink.

  As illustrated in FIG. 2A, when the terminal 1-1 radiates a calibration test signal CS that is a test signal for calibration in the downlink time zone, the terminal 1-2 transmits the downlink from the base station 2. If you are receiving data on, there is a risk of significant interference. In particular, since many people use mobile communication near stations and urban areas where many people are crowded, the calibration test signal of one terminal may interfere with many nearby terminals. As a result, the communication reception quality of the peripheral terminals is greatly deteriorated, which may seriously affect the wireless communication service.

  On the other hand, as shown in FIG. 2-2, when the terminal 1-1 radiates the calibration test signal CS in the uplink time zone, the terminal 1-2 may transmit a signal. Signals are not received and are not affected by interference. In this case, the base station 2 may receive the calibration test signal CS from the terminal 1-1, but here, the terminal 1-1 has a certain distance from the base station 2, and the base station 2 Assume that the reaching interference power is very small. As a result, when the terminal 1-1 performs calibration in a time zone other than the downlink, particularly in the uplink, interference that the calibration test signal has on other communications can be suppressed to a very low level. In the present embodiment, the terminal performs calibration in the uplink to prevent other communication quality degradation.

In the actual environment, it can be seen that the distance between the terminal 1-1 and the base station 2 is somewhat distant from each other for the following two reasons, and the terminal 1-1 and the terminal 1-2 are likely to be close to each other.
1) The base station is usually installed at a higher position than the terminal, and the frequency at which the terminal is located in the vicinity of the base station is low.
2) There are many terminals in the cell supported by the base station, and the terminals are often used at the same height. Therefore, there are a large number of terminals, particularly in stations and urban areas, and there is a high probability that they are located near each other.

  In the TDD scheme, there are time zones such as guard time in addition to downlink and uplink. Therefore, “time zone other than downlink” includes a guard time in addition to the uplink time zone. In the present embodiment, the case where the terminal performs calibration in the uplink is mainly described in order to simplify the description, but the calibration may be performed in the guard time.

  Next, the operation of this embodiment will be described with reference to FIG. The terminal 1-1 first receives a beacon signal or a pilot signal transmitted from the base station 2 by the antenna 11-1, and the signal receiving unit 12-1 performs a predetermined reception process on the received signal. The frame detection unit 14 performs uplink and downlink frame detection on the processed signal, and establishes synchronization with the base station 2. Many methods are conventionally known for frame detection, and any method may be used.

  When the frame detection unit 14 detects a frame and establishes frame synchronization with the base station 2, the frame detection unit 14 detects and notifies an uplink frame to the calibration control unit 15 (in the uplink time zone). The calibration control unit 15 determines the calibration start timing based on the notification, and the signal transmission units 13-1 and 13-2 and the signal reception unit 12 start the calibration. -1,12-2 are instructed. Here, the calibration time zone is arbitrarily selected from the uplink time zone, and the frame detection unit 14 detects and notifies the uplink frame, but this is not limitative. Instead, if it is a time zone other than the downlink frame, another time zone may be detected and notified. For example, when calibration is performed in the guard time zone, the frame detection unit 14 may notify the calibration control unit 15 of the guard time zone.

  Specifically, as an instruction to start calibration, the calibration control unit 15 instructs the signal transmission units 13-1 and 13-2 to transmit a calibration test signal. Then, the antennas 11-1 and 11-2 receive the transmitted calibration test signals, and the signals received by the signal receiving units 12-1 and 12-2 are received. The calibration control unit 15 acquires the received signal from the signal reception units 12-1 and 12-2 as a response to the calibration test signal, and maintains a reversible propagation path on the uplink and downlink based on the response. Calculate an appropriate correction factor. Many calibration methods (calibration procedures, correction coefficient calculation methods, etc.) have been conventionally known, and any method may be used.

  Although the example in which the terminal 1-1 autonomously performs calibration based on the frame detection performed by itself is shown here, the base station 2 notifies the use timing of the calibration of the terminal 1-1 to The station 2 may control the calibration timing. In this case, for example, the terminal 1-1 transmits a calibration request signal to the base station 2, the base station 2 notifies the terminal 1-1 of the timing for executing the calibration as a control signal, and the terminal 1-1. Calibration may be executed at the timing when the instruction is issued.

  Thus, in the present embodiment, the frame detection unit 14 of the terminal 1-1 performs calibration in the uplink time zone. For this reason, the terminal 1-1 can perform calibration while keeping interference on other communications within a small range, and can perform calibration while avoiding a serious influence on the operation of the wireless communication system. Can do. Moreover, since interference can be reduced, the transmission power of other communication apparatuses can be reduced, and as a result, the lifetime can be extended.

  In the present embodiment, the terminal 1-1 has been described as an example. However, if the same configuration as that of the terminal 1-1 is provided and the operation similar to the operation of the present embodiment is performed, the operation will be described. The present invention can also be applied to various wireless communication apparatuses.

  In the present embodiment, the TDD scheme has been described as an example, but the present invention can also be applied to a wireless local area network (LAN) or the like. Furthermore, although the present embodiment has been described assuming antenna calibration, the same method can be applied to other types of calibration (for example, calibration for circuit characteristic correction). In this way, any adaptive environment may be used as long as the principle of the present embodiment is maintained.

Embodiment 2. FIG.
FIG. 3 is a diagram for explaining the calibration execution timing of the second embodiment of the wireless communication apparatus according to the present invention. The configuration of the wireless communication apparatus of this embodiment is the same as that of the first embodiment. Components having the same functions as those in Embodiment 1 are described with the same reference numerals as those in FIG. Hereinafter, a different part from Embodiment 1 is demonstrated.

  In many radio systems using the TDD system, guard time exists in addition to the downlink and uplink. In this guard time, the downlink signal transmitted from the base station propagates in the cell, the terminal switches the circuit from the downlink signal reception circuit to the uplink signal transmission circuit, and the terminal transmits the uplink signal to the base station. It is provided to ensure the time to reach. In the guard time zone (the guard time transmission time zone), the base station does not transmit or receive normal signals.

  Therefore, in the present embodiment, the terminal 1-1 performs calibration using the TDD guard time zone. If the terminal 1-1 calibrates using the guard time zone, since the terminal 1-2 also has the same guard time zone, the calibration test signal CS of the terminal 1-1 is an interference in signal reception of the terminal 1-2. It will not be. Further, since the base station 2 does not receive signals in the guard time zone, the calibration test signal CS of the terminal 1-1 does not interfere with signal reception of the base station 2. As described above, the terminal 1-1 performs the calibration in the guard time period, so that the calibration can be performed without causing interference to other communication.

  Also, in this embodiment, as shown in FIG. 3, in consideration of propagation delay and the like, when there is a guard time zone between the downlink time zone and the uplink time zone, the downlink time zone The calibration test signal CS is transmitted during the period from when the last transmitted downlink sync signal DS reaches the terminal 1-2 to when the uplink signal US at the beginning of the uplink time zone is transmitted from the terminal 1-2. Send.

  Although the operation of the present embodiment is the same as that of the first embodiment, the frame detection unit 14 is in the guard time zone instead of notifying the calibration control unit 15 that it is an uplink frame. To be notified. And the calibration control part 15 will start a calibration similarly to Embodiment 1, if this notification is received.

  FIG. 4 is a diagram illustrating an example when this embodiment is applied to an OFDMA (Orthogonal Frequency Division Multiple Access) scheme. For example, the 3GPP (Third Generation Partnership Project) wireless standard “Evolved Universal Terrestrial Radio Access (E-UTRA) Physical Channels and Modulation (Release 8)”, 3GPP TS 36.211 V8.2.0, 2008-03 When used, the time for OFDM symbols is set as the guard time.

  In order to execute calibration within the guard time zone, in this embodiment, as shown in FIG. 4, a calibration signal format 30 that is a calibration signal format having a symbol time shorter than the guard time is set. . In the calibration signal format 30, the OFDM symbol time Δt2 is set shorter than the OFDM symbol time Δt1 during data transmission. In the calibration signal format 30, the bandwidth Δf2 per subcarrier is set larger than the OFDM subcarrier width Δf1 during data transmission.

  Thus, in this embodiment, calibration is performed by performing channel measurement between antennas using known signals in which subcarriers are arranged at wide intervals in the frequency direction. The antenna calibration is intended to compensate the transmission / reception analog characteristics for each antenna, but the frequency characteristics of the transmission / reception analog circuit are substantially the same even when the band is widened. Therefore, necessary characteristics can be acquired even if calibration is performed using subcarriers having a wider frequency width than OFDMA subcarriers during normal data transmission.

  Note that this calibration format is in the form of an OFDM signal, and signal generation and signal reception can be performed using the same transmitter and reception as in normal data transmission. For example, a calibration signal can be generated by performing processing by increasing the clock speed of a transmission unit and a reception unit that perform normal data transmission to several times that of normal data transmission / reception.

  As described above, when an OFDM signal is used for calibration, a part of the same transmission / reception circuit as that used for data transmission / reception can be used for the calibration process. Furthermore, by setting the OFDM signal symbol time to be shorter than the guard time, calibration can be performed within the guard time.

  In addition, although the example which uses the guard time at the time of changing from a downlink to an uplink was shown in this Embodiment using FIG. 3, the guard time at the time of changing from an uplink to a downlink can also be used. FIG. 5 is a diagram illustrating an example in which calibration is performed during a guard time when changing from uplink to downlink.

  As described above, in this embodiment, when the TDD method is adopted, the calibration is executed within the guard time. For this reason, the terminal 1-1 can perform calibration while suppressing the influence on other communications to be smaller than that of the first embodiment.

Embodiment 3 FIG.
FIG. 6 is a diagram for explaining the calibration execution timing of the wireless communication apparatus according to the third embodiment of the present invention. The configuration of the wireless communication apparatus of this embodiment is the same as that of Embodiment 1, but in this embodiment, an example in which the wireless communication apparatus is a base station will be described. In the present embodiment, the base station has the same configuration as that of the terminal 1-1 of the first embodiment, and the operation related to the calibration of the terminal 1-1 of the second embodiment is the same as that of the base station of the present embodiment. Will do.

  In the second embodiment, the case where the terminal 1-1 performs calibration is shown, but the same processing can be applied to the base station 2 as well. That is, the base station 2 can perform self-calibration by emitting a calibration test signal during the guard time period.

  As shown in FIG. 6, the base station transmits a calibration test signal CS in a guard time zone between a downlink time zone and an uplink time zone. Even if the base station radiates the calibration test signal CS1 immediately after the start in the guard time zone and the radiated power reaches the terminal, the radiated power reaches after the terminal receives the downlink signal DS. Further, when the base station radiates the calibration test signal CS2 in the vicinity of the end point within the guard time zone, the calibration test signal CS2 may arrive at the terminal after the terminal transmits the uplink signal US. However, no problem occurs in the reception performance of the terminal.

  As described above, in this embodiment, the base station performs calibration in the guard time zone. For this reason, the base station can perform self-calibration without affecting the signal reception of the terminal. Conventionally, a time zone dedicated to calibration was required, but in this embodiment, calibration can be performed without preparing radio resources dedicated to calibration, and the operation of the radio communication system is made more efficient. it can.

Embodiment 4 FIG.
FIG. 7 is a diagram for explaining a calibration method according to the fourth embodiment of the wireless communication apparatus according to the present invention. The configuration of the wireless communication apparatus of the present embodiment is the same as that of the first and second embodiments.

  Usually, the terminal calibration test signal is weak radiated power, and if there is another radio (terminal, base station, etc.) at a short distance from the terminal, it may affect communication. In a radio located at a distance far from the received power, the received power is negligible. Therefore, in this embodiment, when the terminal is located near the base station, calibration is performed using the guard time zone, and when the terminal is located far from the base station, any other than the downlink is performed. Calibration is performed using the time zone. That is, the terminal of the present embodiment has both functions of the frame detection unit 14 of the terminal 1 of the first embodiment and the frame detection unit of the terminal of the second embodiment, and the calibration of the present embodiment. The control unit has the function of the calibration control unit 15 of the first embodiment and, as will be described later, the operation of the first embodiment and the second embodiment based on a parameter proportional to the distance from the base station or the propagation time. Switch the operation.

  For example, since area A1 in FIG. 7 is an area within a predetermined distance from base station 2 and is close to the base station, terminal 1-1 is guarded in the same manner as in the embodiment when it exists in area A1. Calibration is performed in the time zone, and in the area A2 outside the area A1, the terminal 1-1 performs calibration in the uplink time zone.

  In this embodiment, since a terminal close to the base station performs calibration with a guard time, it does not interfere with other communications. Also, even if a terminal that is located at a distance from the base station performs calibration in the uplink time zone, the interference power received by the base station is at a level that can be ignored. Calibration can be performed, and the degree of freedom in selecting calibration timing is increased. For this reason, when a plurality of terminals perform calibration, it is possible to distribute the time period in which the terminal performs calibration including the uplink time period. As a result, when a plurality of terminals execute calibration at the same time, it is possible to reduce the possibility of occurrence of phenomena that interfere with each other.

  Next, a calibration timing control method according to the present embodiment will be described. FIG. 8 is a flowchart illustrating an example of the procedure of the calibration timing control method according to the present embodiment. Here, the parameter d proportional to the distance between the base station and the terminal or the propagation time is measured. For example, in response to a pilot signal received on the downlink, the terminal transmits a signal on the uplink, the base station measures the time width from the pilot signal transmission to the reception of the uplink signal, and the measured value of the time width is used as the measurement value. It can be used as parameter d. In addition, the parameter d proportional to the distance or the propagation time can be measured by various conventionally known methods.

  First, the base station measures the parameter d, and notifies the parameter d to the terminal (step S11). The calibration control unit of the terminal determines whether or not the parameter d is less than a predetermined threshold D (step S12). When it is determined that d is less than D (step S12 Yes), the terminal performs calibration in the guard time zone as in the second embodiment (step S13). If it is determined that d is equal to or greater than D (No in step S12), calibration is performed on the uplink as in the first embodiment (step S14). By such control, the timing for performing calibration can be changed according to the position of the terminal.

  In this embodiment, the base station measures d and notifies the terminal. However, the present invention is not limited to this, and the base station holds d, and the base station has d less than the threshold value D. It may be determined whether the calibration is performed in the guard time zone or the uplink time zone, and the timing for performing calibration may be instructed to the terminal by the control signal. In this case, when a plurality of terminals perform calibration, it is possible to change the timing of performing calibration for each terminal and distribute the instructions. In addition, in the case of OFDMA (Orthogonal Frequency Division Multiple Access), the base station can also instruct not only the temporal timing but also the frequency band used for calibration.

  Thus, in this embodiment, the base station measures the parameter d proportional to the distance between the base station and the terminal or the propagation time and notifies the terminal, and the terminal performs calibration based on d. The timing was decided. For this reason, compared with Embodiment 2, the freedom degree of the timing of calibration can be raised.

Embodiment 5 FIG.
FIG. 9 is a diagram for explaining the calibration execution method of the fifth embodiment of the wireless communication apparatus according to the present invention. In the first, second, and fourth embodiments, the terminal performs calibration in the uplink or guard time, thereby reducing the possibility of interference occurring in other communications due to the calibration test signal. However, in the case of the first embodiment or the fourth embodiment, as shown in FIG. 9, the terminal 1-2 exists in the vicinity of the terminal 1-1 that is transmitting the calibration test signal CS, and the terminal 1-2. May transmit the uplink signal US. In this case, the transmission signal of the terminal 1-2 interferes with the calibration of the terminal 1-1, and the channel measurement when the terminal 1-1 performs the calibration cannot be performed with high accuracy. The calibration accuracy may be degraded.

  In order to solve this problem, in this embodiment, the terminal transmits a calibration test signal in a wide band. FIG. 10 is a diagram illustrating an example of the transmission frequency band of the calibration test signal according to the present embodiment. As shown in FIG. 10, the calibration signal is transmitted with a calibration signal bandwidth 32 wider than the transmission band 31 which is the maximum frequency band of communication of the normal terminal 1-2.

  When the terminal 1-1 performs calibration while the terminal 1-2 is performing signal transmission, it receives interference from the transmission signal from the terminal 1-2 in the frequency band overlapping with the signal being transmitted. Since there is no transmission signal from the terminal 1-2 in the frequency band (for example, in the example of FIG. 10, the portion that does not overlap the transmission band 31 of the calibration signal bandwidth 32), the terminal 1-2 is calibrated with high accuracy. A test signal can be received. Further, the terminal 1-1 transmits a wideband calibration test signal, and performs calibration by selecting a frequency band with high reception quality among the portions of the calibration signal bandwidth 32 that do not overlap the transmission band 31. By doing so, more accurate calibration can be executed. Normally, the analog transmission / reception characteristics of each antenna have the same characteristics in a wide band, and therefore, the calibration coefficient can be used for other frequency bands by performing calibration at one frequency in the wide band.

  Note that the configuration and operation of the terminal 1-1 of the present embodiment is the same as that of the embodiment except that the transmission frequency band of the calibration test signal is widened and the frequency band of high reception quality is selected to perform the calibration. The same as in Embodiment 1 or Embodiment 4.

  Here, since the calibration test signal of the terminal 1-1 has low transmission power, the terminal can transmit the calibration test signal in a wide band. On the other hand, the terminal 1-2 transmits a signal with a large transmission power in a specific frequency band in order to transmit a communication signal to the base station. Normally, the maximum transmission power of the terminal is limited by the performance of the transmission amplifier, and it is difficult for the terminal 1-2 to transmit a broadband and high-power signal at a time. Therefore, if the terminal 1-1 transmits a calibration test signal in a band wider than the maximum bandwidth that a normal terminal can use for communication, it is possible to perform highly accurate channel measurement in a part of the frequency band. Increases nature.

  As described above, in the present embodiment, the calibration test signal is transmitted in a frequency band wider than the maximum frequency bandwidth that the terminal can transmit during normal uplink signal communication. For this reason, it is possible to perform calibration with higher accuracy than in the first or fourth embodiment when other communication devices exist nearby. Furthermore, in the present embodiment, the terminal 1-1 selects a frequency with high reception quality and performs calibration. For this reason, calibration with higher accuracy is possible.

Embodiment 6 FIG.
FIG. 11: is a figure which shows the function structural example of Embodiment 6 of the radio | wireless communications system concerning this invention. As shown in FIG. 11, the radio communication system of the present embodiment includes a terminal 1a and a base station 2a. The terminal 1a is the terminal of the first embodiment except that the calibration control unit 15 of the terminal 1 of the first embodiment is replaced with the calibration control unit 15a, the frame detection unit 14 is deleted, and a control signal receiving unit 16 is added. Same as 1. The base station 2a of the present embodiment includes an antenna 21, a signal receiving unit 22 that performs a predetermined reception process on a signal received by the antenna 21, a signal transmission unit 23 that performs a predetermined transmission process on a transmission signal, A radio resource control unit 24 is provided. Components having the same functions as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown so far, the radio wave radiated at the time of calibration of the terminal is weak, but it interferes when another radio exists near the terminal. Therefore, in the present embodiment, the base station 2a allocates calibration radio resources to the terminal 1a. Specifically, radio resources (frequency or time) that are not used for signal transmission such as data packet transmission and control signal are allocated to the calibration desired terminal. A terminal to which a radio resource is assigned performs calibration using the radio resource.

  FIG. 12 is a flowchart illustrating an example of a processing procedure of the calibration method according to the present embodiment. The operation of this embodiment will be described with reference to FIGS. First, the radio resource control unit 24 of the base station 2a allocates uplink and downlink radio resources (frequency band, communication time, etc.), and determines the frequency or time at which each terminal transmits and receives data. If there is a remaining radio resource that is not used for data transmission among all the radio resources that can be used by this communication system, the remaining radio resource is allocated for terminal calibration (step S21). The signal transmission unit 23 of the base station 2a acquires a radio resource assigned to the terminal from the radio resource control unit 24 via the signal reception unit 22, and a terminal corresponding to control information including identification information (ID) corresponding to the radio resource. Is notified by transmitting via the antenna 21 (step S22).

  In the terminal 1a, the control signal receiving unit 16 receives the control information via the antenna 11-1 and the signal receiving unit 12-1, extracts the ID of the radio resource to be calibrated, and uses the radio resource corresponding to the ID. Calibration is performed (step S23). Normally, the analog transmission / reception characteristics of each antenna have the same characteristics in a wide band. Therefore, when calibration is performed at one frequency in the wide band, the correction coefficient obtained by the calibration can be used in other frequency bands. .

  In this way, the base station designates the radio resources for calibration to the terminal, and the base station performs calibration using the radio resources, so that the base station can control so as not to interfere with other communications. it can.

  It is also possible to allocate a TDD downlink radio resource by the above-described radio resource allocation. Although the TDD scheme has been described so far, the radio resource allocation control according to the present embodiment is applicable to the FDD scheme. For calibration in the FDD system, for example, as disclosed in “Publication of Japanese Patent Application Laid-Open No. 2006-279668”, antenna calibration can be performed using two frequencies of the uplink and downlink. Therefore, by allocating uplink / downlink radio resources (frequencies) used for transmitting the calibration test signal, the terminal can perform smooth calibration while avoiding the influence on other communications.

  Note that the base station may assign an uplink time zone or a guard time zone to a terminal in the TDD scheme, and the terminal may perform calibration by the same operation as in the first, second, or fourth embodiment.

  When a plurality of terminals desire calibration, the base station can allocate different radio resources to the individual terminals. By performing such control, it is possible to avoid a situation in which a plurality of terminals use the same radio resource and the calibration test signals interfere with each other.

  Further, the characteristics of the analog transmission / reception circuit that performs correction by antenna calibration vary slowly in time depending on the temperature. The fluctuation is sufficiently slow compared with the communication control cycle, and the calibration may be performed in a long cycle of 1 second or more. Depending on the case, a long period of 1 minute or more or 10 minutes or more may be used. Thus, the calibration cycle is sufficiently longer than the normal communication packet allocation cycle (for example, several tens of ms unit).

  Therefore, when many terminals desire calibration, different terminals can perform calibration for each frame, and the same terminal can be calibrated at a constant period. FIG. 13 is a diagram illustrating an example in which time for calibration is assigned to a plurality of terminals for each frame. The allocation frame 33 indicates a frame allocated for calibration to the terminal A (one of the terminals 1a), and the allocation frame 34 is used for calibration to the terminal B (one of the terminals 1a other than the terminal A). This is shown in the frame assigned to.

  Although an example of assigning in units of frames has been described here, calibration time may be periodically assigned to different terminals in units of guard time. In this case, the base station 2a notifies the terminal 1a of the frame number (or ID of the guard time located at the head of the frame) and the calibration cycle (number of frames) for the first calibration as control signals. And the terminal 1a can grasp | ascertain the time timing which performs the 1st calibration, and can obtain the calibration timing after the 2nd time by adding the period notified to the 1st time timing.

  As described above, in the present embodiment, the base station 2a allocates the remaining radio resources that are not used for communication to the terminal 1a as radio resources for calibration. For this reason, it is possible to avoid the influence of calibration on communication and perform calibration by efficiently using radio resources. In addition, since radio resources can be allocated to each terminal, it is possible to avoid a plurality of terminals from using the same radio resource and to avoid a phenomenon in which calibration test signals interfere with each other.

  As described above, the wireless communication device, the wireless communication system, and the calibration method according to the present invention are useful for a wireless communication system that performs self-calibration, and are particularly suitable for a wireless communication system in which a wireless communication device is close. .

It is a figure which shows the function structural example of Embodiment 1 of the radio | wireless communication apparatus concerning this invention. It is a figure which shows the implementation timing of self-calibration, and the influence on another terminal. It is a figure which shows the implementation timing of self-calibration, and the influence on another terminal. It is a figure for demonstrating the calibration implementation timing of Embodiment 2 of the radio | wireless communication apparatus concerning this invention. It is a figure which shows an example in the case of applying this Embodiment to an OFDMA system. It is a figure which shows the example which performs a calibration in the guard time at the time of changing from an uplink to a downlink. It is a figure for demonstrating the calibration implementation timing of Embodiment 3 of the radio | wireless communication apparatus concerning this invention. It is a figure for demonstrating the calibration method of Embodiment 4 of the radio | wireless communication apparatus concerning this invention. 14 is a flowchart illustrating an example of a procedure of a calibration timing control method according to the fourth embodiment. It is a figure for demonstrating the calibration implementation method of Embodiment 5 of the radio | wireless communication apparatus concerning this invention. It is a figure which shows an example of the transmission frequency band of a calibration test signal. It is a figure which shows the function structural example of Embodiment 6 of the radio | wireless communications system concerning this invention. 22 is a flowchart illustrating an example of a processing procedure of a calibration method according to a sixth embodiment. It is a figure which shows the example which allocated the time for calibration to the some terminal for every flame | frame.

Explanation of symbols

1, 1-1, 1-2, 1a terminal 2, 2a base station 11-1, 11-2, 21 antenna 12-1, 12-2 signal reception unit 13-1, 13-2 signal transmission unit 14 frame detection Unit 15, 15a Calibration control unit 16 Control signal receiving unit 22 Signal receiving unit 23 Signal transmitting unit 24 Radio resource control unit

Claims (4)

A wireless communication device having the plurality of antennas for performing self-calibration between a plurality of antennas,
When adopting OFDM system as digital modulation system,
Radio communications device you and performs self-calibration using OFDM symbols with short symbol time than OFDM symbol during data communication as the calibration test signal. The wireless communication apparatus according to claim 1, wherein in the self-calibration, self-calibration is performed using a calibration test signal having a frequency band wider than a frequency band of a transmission signal during data communication. A first selection mode in which the self-calibration is performed in an uplink signal transmission time zone, and a second selection mode in which a self-calibration is performed in a guard time zone between the uplink and the downlink , the toggle on the basis of the proportional parameter distance wireless communication apparatus according to claim 1 or claim 2, characterized in. The radio communication apparatus according to claim 1 or 2 , wherein a frequency band with good reception quality is selected based on the calibration test signal, and the selected frequency band is used for the self-calibration.

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